The SAUR gene family: the plant’s toolbox for adaptation of growth and development

The family of small auxin up-regulated RNA (SAUR) genes is a family of auxin-responsive genes with ~60–140 members in most higher plant species. Despite the early discovery of their auxin responsiveness, their function and modeof action remained unknown for a long time. In recent years, the importance of SAUR genes in the regulation of dynamic and adaptive growth, and the molecular mechanisms by which SAUR proteins act are increasingly well understood. SAURs play a central role in auxin-induced acid growth, but can also act independently of auxin, tissue specifically regulated by various other hormone pathways and transcription factors. In this review, we summarize recent advances in the characterization of the SAUR genes in Arabidopsis and other plant species. We particularly elaborate on their capacity to fine-tune growth in response to internal and external signals, and discuss the breakthroughs in understanding the mode of action of SAURs in relation to their complex regulation

Divergent regulation of Arabidopsis SAUR genes: a focus on the SAUR10-clade

Background Small Auxin-Upregulated RNA (SAUR) genes encode growth regulators that induce cell elongation. Arabidopsis contains more than 70 SAUR genes, of which the growth-promoting function has been unveiled in seedlings, while their role in other tissues remained largely unknown. Here, we focus on the regulatory regions of Arabidopsis SAUR genes, to predict the processes in which they play a role, and understand the dynamics of plant growth. Results In this study, we characterized in detail the entire SAUR10-clade: SAUR8, SAUR9, SAUR10, SAUR12, SAUR16, SAUR50, SAUR51 and SAUR54. Overexpression analysis revealed that the different proteins fulfil similar functions, while the SAUR expression patterns were highly diverse, showing expression throughout plant development in a variety of tissues. In addition, the response to application of different hormones largely varied between the different genes. These tissue-specific and hormone-specific responses could be linked to transcription factor binding sites using in silico analyses. These analyses also supported the existence of two groups of SAURs in Arabidopsis: Class I genes can be induced by combinatorial action of ARF-BZR-PIF transcription factors, while Class II genes are not regulated by auxin. Conclusions SAUR10-clade genes generally induce cell-elongation, but exhibit diverse expression patterns and responses to hormones. Our experimental and in silico analyses suggest that transcription factors involved in plant development determine the tissue specific expression of the different SAUR genes, whereas the amplitude of this expression can often be controlled by hormone response transcription factors. This allows the plant to fine tune growth in a variety of tissues in response to internal and external signals

Divergent regulation of Arabidopsis SAUR genes : A focus on the SAUR10-clade

Background: Small Auxin-Upregulated RNA (SAUR) genes encode growth regulators that induce cell elongation. Arabidopsis contains more than 70 SAUR genes, of which the growth-promoting function has been unveiled in seedlings, while their role in other tissues remained largely unknown. Here, we focus on the regulatory regions of Arabidopsis SAUR genes, to predict the processes in which they play a role, and understand the dynamics of plant growth. Results: In this study, we characterized in detail the entire SAUR10-clade: SAUR8, SAUR9, SAUR10, SAUR12, SAUR16, SAUR50, SAUR51 and SAUR54. Overexpression analysis revealed that the different proteins fulfil similar functions, while the SAUR expression patterns were highly diverse, showing expression throughout plant development in a variety of tissues. In addition, the response to application of different hormones largely varied between the different genes. These tissue-specific and hormone-specific responses could be linked to transcription factor binding sites using in silico analyses. These analyses also supported the existence of two groups of SAURs in Arabidopsis: Class I genes can be induced by combinatorial action of ARF-BZR-PIF transcription factors, while Class II genes are not regulated by auxin. Conclusions:SAUR10-clade genes generally induce cell-elongation, but exhibit diverse expression patterns and responses to hormones. Our experimental and in silico analyses suggest that transcription factors involved in plant development determine the tissue specific expression of the different SAUR genes, whereas the amplitude of this expression can often be controlled by hormone response transcription factors. This allows the plant to fine tune growth in a variety of tissues in response to internal and external signals.</p

Divergent regulation of Arabidopsis SAUR genes : A focus on the SAUR10-clade

Background: Small Auxin-Upregulated RNA (SAUR) genes encode growth regulators that induce cell elongation. Arabidopsis contains more than 70 SAUR genes, of which the growth-promoting function has been unveiled in seedlings, while their role in other tissues remained largely unknown. Here, we focus on the regulatory regions of Arabidopsis SAUR genes, to predict the processes in which they play a role, and understand the dynamics of plant growth. Results: In this study, we characterized in detail the entire SAUR10-clade: SAUR8, SAUR9, SAUR10, SAUR12, SAUR16, SAUR50, SAUR51 and SAUR54. Overexpression analysis revealed that the different proteins fulfil similar functions, while the SAUR expression patterns were highly diverse, showing expression throughout plant development in a variety of tissues. In addition, the response to application of different hormones largely varied between the different genes. These tissue-specific and hormone-specific responses could be linked to transcription factor binding sites using in silico analyses. These analyses also supported the existence of two groups of SAURs in Arabidopsis: Class I genes can be induced by combinatorial action of ARF-BZR-PIF transcription factors, while Class II genes are not regulated by auxin. Conclusions:SAUR10-clade genes generally induce cell-elongation, but exhibit diverse expression patterns and responses to hormones. Our experimental and in silico analyses suggest that transcription factors involved in plant development determine the tissue specific expression of the different SAUR genes, whereas the amplitude of this expression can often be controlled by hormone response transcription factors. This allows the plant to fine tune growth in a variety of tissues in response to internal and external signals.</p

Additional file 2: Table S1. of Divergent regulation of Arabidopsis SAUR genes: a focus on the SAUR10-clade

Overview of published data showing the response of the individual Arabidopsis SAURs to auxin and BR. Table S2. Classes of SAUR genes based on Additional file 2: Table S1. Table S3. Primer sequences. (XLSX 38 kb

Additional file 5: Figure S4. of Divergent regulation of Arabidopsis SAUR genes: a focus on the SAUR10-clade

Dynamics of IAA/BR induction (PDF 132 kb

Additional file 7: Figure S6. of Divergent regulation of Arabidopsis SAUR genes: a focus on the SAUR10-clade

The location of GUS expression does not change after IAA-BR treatment. (PDF 373 kb

Additional file 4: Figure S3. of Divergent regulation of Arabidopsis SAUR genes: a focus on the SAUR10-clade

Expression patterns of the pSAUR:GUS lines. (PDF 869 kb